Needle Thread Research Articles

Dynamics of lockstitch sewing process

During high speed sewing, the needle thread is exposed to dynamic loading, short strike loading, inertia forces, friction, rubbing, force of check spring, bending, pressure, friction, impact, shock and thermal influence. The dynamic thread loading/tension alters throughout the stitch formation cycle and along its passage through the machine. The greatest tensile force occurs at the moment of stitch stretching, when the take up lever pulls for required thread length through the tension regulator. These stresses act on the thread repeatedly and the thread passes 50-80 times through the fabric, the needle eye and the bobbin case mechanism, before getting incorporated into the seam, which result in upto 40% loss in tensile strength of the sewing thread. This damage in the sewing thread adversely affects its processing and functional performance. In this paper, the contribution of dynamic loading, passage through needle and fabric, and bobbin thread interaction in the loss in tensile properties has been studied. It is observed that the loss in tensile properties occurs mainly due to the bobbin thread interaction. Dynamic loading due to the action of take up lever also causes substantial loss in tenacity and breaking elongation of cotton threads.

Effect of Some Fabric and Sewing Conditions on Apparel Seam Characteristics

Many previous studies showed that seam appearance as well as performance depends on the interrelationship of fabrics, threads, and the stitch/seam selection and lastly on the sewing conditions, which include the needle size, needle thread tension, stitch density, and the appropriate operation and maintenance of the sewing machine. Present investigation elucidates the effect of blend composition, sewing thread size, and sewing needle parameters on garment seam characteristics (i.e., seam strength, seam strength efficiency, seam puckering, seam stiffness, and drape coefficient). The seam quality characterization is studied through the L9 orthogonal design methodology. In good quality apparels, compatibility of the seams with the functional requirement is very important for serviceability and life of the apparel. Reversibility as well as repairing of seams in the apparel is very limited in the condition of seam failure. Seam strength efficiency is higher for the uniform fiber matrix in the structure of fabrics. The polyester dominated suiting fabrics give minimum seam stiffness because polyester component has low flexural rigidity. The cotton dominated suiting fabrics have less seam puckering due to increase in fabric stiffness.

An Approach to Seam Strength Prediction Using Residual Thread Strength

Owing to a high amount of stress, seam failure in workwear fabrics makes the fabric unsuitable although the fabric strength is high. It is therefore important to predict the seam strength to ascertain the performance of the garments during use and determine the required thread strength and stitch density to match the required seam strength. In all of the earlier predictive equations, seam strength is predicted from thread strength and stitch density along with some multiplicative factors. During the sewing process, a substantial loss in needle thread strength occurs; therefore, the thread becomes weaker than expected after incorporation into the seam. In this paper, the effects of various machine and process parameters are studied on thread strength loss and seam strength. The seam strength is predicted from the loop strength after considering the loss in thread strength. It is observed that higher seam strengths are observed when stronger threads are used for sewing. Loss in thread strength has a significant influence on the seam strength. Seam strength can be predicted using stitch density and thread loop strength, by considering the loss in thread strength during the sewing process. A closer match between predicted and experimental seam strength is possible.

EFFECT OF THREAD STRUCTURE ON TENSION PEAKS DURING LOCK STITCH SEWING

Abstract A dynamic sewing tension study was carried out with a tension probe on sewing threads with different structures, physical and tensile characteristics in a single needle lock stitch sewing machine. The needle thread recorded four major tension peaks corresponding to events occurring during sewing; bobbin thread withdrawal, stitch tightening, needle piercing the fabric and tightening of the needle thread around the shuttle, among which stitch tightening caused the maximum tension for all threads. Polyester filament and spun polyester threads exhibited the highest and lowest tightening tension, respectively. Multiple regression analysis showed that pre-tension and elastic modulus show positive influences while tex, bending, rigidity and compressibility of threads show negative effects on tension peaks during tightening and needle piercing. Sewing speed shows a positive impact only on the tension peak due to needle piercing. Pre-tension showed a prominent influence on tension peaks on all threads while the number of fabric layers failed to show any effect.

A SIMPLE SYSTEM FOR THE ONLINE DETECTION OF SKIP/LOOP STITCHES IN SINGLE NEEDLE LOCKSTITCH SEWING MACHINES

Abstract In single needle lockstitch sewing machines, the needle thread consumption of 10 normal stitches for a fabric with a particular number of layers at a particular stitches per unit length is manually measured kept as a reference value. If the value of needle thread consumed per stitch is very small, the length of thread consumed per 10 stitches is used as a comparing value. The actual thread consumed for every 10 stitches is measured online by a rotary optical encoder sensor by converting the angular movement into the linear movement of the thread and continually compared with the reference value. If the online measured length is more or less a buzzer sounds to indicate the variation. The counting of every stitch formed is undertaken by a proximity sensor by sensing the protrusion in the hand wheel of the machine, which rotates once for every rotation.

Effect of Workwear Fabric Characteristics on the Changes in Tensile Properties of Sewing Threads after Sewing

During sewing at high speed, the needle thread is subjected to repeated tensile stresses, heat, bending, pressure, torsion and wearing. These stresses act on the thread repeatedly and the thread passes 50–80 times through the fabric, the needle eye and the bobbin case mechanism, before getting incorporated into the seam. As a result both the sewing thread and the yarns in the fabric get abraded/ severed during the seaming process. A number of researchers observed that there could be 30% to 40% strength loss in the cotton needle thread after sewing. The extent of damage becomes more critical if the fabric being used is of a dense, thick and heavy construction. A number of studies have been carried out on thread strength loss after sewing, but the impact of fabric characteristics on thread strength loss is still unexplored. In this paper, the effect of weight and fabric composition of workwear fabrics, on the changes in the tenacity, breaking elongation and initial modulus of the needle thread has been studied. The tenacity and breaking elongation loss increase with increase in fabric weight for staple threads and remain unchanged for core spun threads. The loss in initial modulus increases for polyester threads as fabric weight increases, and decreases for cotton thread. When sewn on polyester-cotton fabric of same weight, the cotton thread shows decrease in tenacity and breaking elongation loss, whereas loss in initial modulus increases. The polyester core spun threads show exactly opposite change, i.e. tenacity and elongation loss increase and loss in initial modulus decreases when sewn on polyester-cotton fabric.

Wpływ warunków pracy tarczowego podciągacza nici na charakterystykę ściegu czółenkowego

Analysis of literature described in the dissertation showed the complexity of phenomena of machine stitch creation processes. The reference to the lockstitch proves particularly difficult working conditions of needle thread. Tools forming the stitch (needle, bobbin, needle thread take-up, thread tensioner, transporter of the textile package) cause the weakening of thread inserted into the seam structure, what can lead to thread breakage. Hence, a great attention is paid to the action on thread of stitch forming mechanisms in the sewing machines.A particular role of thread take-up mechanism was stressed during discussing the process of thread control conditions by the take-up in the lockstitch machines. Characteristic working phases of the take-up were distinguished i.e., supplying by the thread and drawing of thread end during the stitch tightening. One has paid the attention to the conditions of interlacement location in the material and the possibility of correcting them by the improving the structure of the thread take-up mechanism. Changing the stitch tightening modelling process was to achieve this aim. So, a physical model, and next a mathematical model of the zone of stitch creation were elaborated. Due to the possibility of configuration of multibarrier take-ups creation a model of the stitch tightening considering the take-up disc was built.The presented results of model research required the experimental verification. The dynamic tensions in threads and the thread strength decrease after the sewing through process as well as a reaction of the take-up to changes thread length in the link of the stitch were studied. Carrying out the experimental analysis required the building the take-up disc installed on the chosen machine. Thus, there is a need for elaboration of the methodology of the take-ups disc designing using genetic algorithms as well as a classical programming in Fortan and C++ languages. The determination of requirement take-up disc configuration was preceded by a definition of the curve of the thread controlled by the take-up disc. Next, one made an estimation of defined curve of the thread controlled by take-up disc with a software called “Take-up disc 2.0” elaborated on the basis of genetic algorithm.The designed and built thread take-up disc allow decreasing peaks of strength of the stitch tightening over twice of the basic value, which is the significant achievement from a technical-technological point of view. Moreover, it causes the decrease of thread breaking strength losses. In the case of the takeup disc, holding the position of the interlacement in the stitch link on the set level requires the extending the part of machine working cycle corresponding to the stitch tightening in comparison to the generally used take-ups.

Studies on the Changes in Tensile Properties of Sewing Thread at Different Sewing Stages

A lockstitch is formed by the interlacement of needle and bobbin threads. During high-speed sewing, needle thread is subjected to repeated tensile stresses, heat, bending, pressure, torsion, and wearing. Therefore, the mechanical properties of thread, which become altered during sewing, are very important for its performance and durability. In order to design a sewing machine and threads for maximum strength retention, it is important to understand how the mechanical properties of the thread change as it progresses through the machine and become incorporated into the seam. In this paper, the tensile properties of the needle thread are measured at four sewing stages: before sewing, after dynamic loading at the tension regulator, after passage through the needle and fabric, and after bobbin thread interaction. Mercerized cotton, polyester staple spun, polyester—cotton core spun, and polyester—polyester core spun threads are used and the contribution of dynamic loading, passage through the needle and fabric, and bobbin thread interaction to the change in tensile properties is analyzed. The loss in tenacity, elongation, and breaking energy for cotton thread is the highest, followed by polyester staple and core spun threads. However, the cotton thread shows lower loss in initial modulus as compared with the other threads. Bobbin thread interaction is mainly responsible for the loss in thread strength, elongation, initial modulus, and breaking energy for all threads, barring breaking elongation in cotton threads. Dynamic loading leads to an increase in the initial modulus for all threads. Passage through the needle and fabric assembly has a relatively small contribution to the reduction in tensile properties.

Effect of high‐speed sewing on the tensile properties of sewing threads at different stages of sewing

PurposeIn this paper, the contribution of dynamic loading, needle and fabric, and the bobbin thread interaction on the changes in the tensile properties of the needle thread are to be investigated.Design/methodology/approachTensile properties of the needle thread have been studied at four sewing stages, namely before being subjected to any loading, after dynamic loading, before bobbin thread interaction and after sewing.FindingsIt is observed that bobbin thread interaction plays a dominant role in the reduction of tensile properties except breaking elongation in cotton threads. Dynamic loading is mainly responsible for reduction in the breaking elongation of cotton threads. During sewing, there is an increase in initial modulus due to the dynamic loading, which is more in the case of cotton threads than polyester threads. However, the impact of dynamic loading on tenacity, breaking elongation and breaking energy is greater for coarser cotton thread. The contribution of bobbin thread interaction is more for fine threads as compared to coarse threads.Practical implicationsSince seam strength is dependent on the thread strength, a reduction in thread strength during sewing will lead to lower seam strength than expected. Therefore, in order to minimize the thread strength reduction, it is important to understand the contribution of different machine elements or processes during sewing. During high‐speed sewing, the dynamic and thermal loading are found to be the major causes of strength reduction of needle thread, which can go up to 30‐40 per cent. However, the extent of strength loss at different sewing stages is unknown.Originality/valueThe study will help in engineering sewing threads, designing of sewing machines and selection of process parameters for controlling loss of useful properties of sewing threads.

THE EFFECTS OF CHECK-SPRING TRAVEL ON LOCKSTITCH SEWING

The stitch formation process of a lockstitch sewing machine has been investigated with the aid of transducers which facilitate real-time monitoring of the sewing cycle. It has been found that increasing the travel of the check-spring by three millimetres from the normal position significantly reduces needle thread consumption per stitch and increases the peak dynamic needle thread tension. This change in lockstitch formation has a profound effect on the geometry of the stitch and the theoretical performance of the stitch under longitudinal load. The ability to reduce static thread tension settings after extending the check-spring travel can be employed as a remedy for tension induced seam pucker.

Objective Evaluation of Seam Pucker Using Artificial Intelligence Part III: Using the Objective Evaluation Method to Analyze the Effects of Sewing Parameters on Seam Pucker

The new objective evaluation method of seam pucker reported in Parts I and II of this study is used to analyze the effects of sewing parameters on seam pucker with five shape parameters in this part of the series. The parameters of sewing thread tension and stitch length are varied. To measure needle and bobbin thread tensions, frames are modified with dial tension gauges, linear guides, and weights. Four lightweight synthetic fabrics are used for seam pucker experiments. The needle and a bobbin. threads are polyester. These experiments show that sewing thread tension affects the wave amplitudes on the puckered surface as well as the objective AATCC seam pucker grade, but has no effect on the wave frequency characterized by the number of wave generating points and the wavelengths. Stitch length influences wave frequency on the seam line as well as AATCC grade, but without influencing wave amplitudes. The effects of stitch length on the shape parameters are quite different from those of sewing thread tension. With the expanded information provided by the five shape parameters of seam pucker, the effects of sewing parameters on seam pucker can be examined in more detail. The new evaluation method could be instrumental in better understanding the cause of seam pucker and its eventual elimination.

本縫ミシンにおける上糸張力と上糸移動量の同時計測法

本縫ミシンにおける上糸張力と上糸移動量の同時計測法

Strength Reduction in and Damage to Fibres during High-speed Sewing in an Industrial Lockstitch Machine

The reduction in the tensile strength of polyester fibres on sewing is studied for threads with different yarn and fibre linear density and tenacity. The strength loss ranges between 4.8% and 8.9% and is much less than that of the sewn threads. The initial modulus of the fibre and the extent of loading during sewing influence the strength reduction. A scanning-electron-microscope (SEM) study of sewn threads and of the constituent fibres shows that the damage is mostly concentrated at the interlacing point of the needle thread in the stitch. Among the various stresses acting on the fibres, bending and surface abrasion are found to be more dominant in causing damage to tbe fibre.

本縫いミシンにおける縫目バランス評価法

A new measuring method of stitch balance for a lockstitch sewing machine is proposed. The stitch balance is estimated by the field of the bobbin thread appeared in a stitch hole. The visual field is measured quantitatively by dots of a picture area which is painted using a personal computer and a image scanner. The method has following special features ; 1) the many data can be processed in a short time, 2) the sewn fabrics is not cut and 3) the estimation is able to be used for a long continuous seam. But there is the problem that the color of the bobbin thread must be different from both one of the needle thread and the sewn fabrics.

The Effects of Sewing Machine Needle and Bobbin Thread Tension on Stitch Balance and Seam Pucker.

We investigated the thread tension of sewing machines in practical conditions by interviewing several sewing engineering experts. Of those interviewed, 80% replied that they rely on their experience and intuition, when they adjust the needle and bobbin thread tension of a sewing machine in order to obtain a well balanced stitch. Bobbin thread tension changes during a pulley rotation and also reeling amount of bobbin thread, even if the other condition is the same. In this study, we tried to clarify the effect of needle and bobbin thread tension on stitch balance and seam puckering. The seamed samples were prepared using the fabrics and sewing machine threads having different mechanical properties. We postulate the following the criteria that when the length of the needle and bobbin thread per unit fabric length are the same, a stitch is well balanced. Needle thread tension should increase if bobbin thread tension raises to obtain a balanced stitch. To achieve a pucker free seam, the thread tension must be maintained as low as possidle. In the above conditions, a large amount of thread is necessary to obtain a good seam. We established the relationship among needle and bobbin thread tension, stitch balance and seam puckering. The effect of physical properties of fabric and sewing thread on the above relationship was also studied.

Sewing Performance of Cotton/ Lycra Knitted Fabrics

This paper describes a computer-based system installed on industrial lockstitch and overlock stitch sewing machines. The system uses commercial hardware and developed software to acquire and analyze the collected signals of needle thread tension, presser foot displacement, presser foot pressure, and needle penetration/withdrawal forces. The effects of sewing speed, needle size, and the number of plies of a fabric sewn together on variations in measured needle penetration and withdrawal forces are in vestigated.

A Study of Positive Needle Thread Feed during Chainstitch Sewing

The paper compares the effect of sewing variables and fabric parameters on the shrinkage of chainstitch (ISO 401) seams sewn by two different thread feeding systems; (a) conventional method; and (b) positive feed.

A Study of Thread Tensions on a Lockstitch Sewing Machine (Part II)

A study of thread tensions on a lockstitch sewing machine was made, measuring simultaneously both the needle and bobbin thread tensions. Investigates the relationship between the peak tensions generated during the experiments and the corresponding seam balance. It was found that under the conditions of the experiments it is possible to define an envelope of conditions under which balanced seams will be obtained.

A Study of Thread Tensions on a Lockstitch Sewing Machine (Part I)

A study of thread tensions on a lockstitch sewing machine was made, measuring simultaneously both the needle and bobbin thread tensions. Experiments were carried out under specified sewing conditions, whereby needle and bobbin thread tensioner adjustment, sewing speed, number of plies, fabric quality and sewing thread quality were varied in order to investigate the effect of these factors on the needle and bobbin thread tensions. The patterns of the thread tension traces obtained were analysed as well as the effect of these factors on the peak tensions detected on both thread tension traces. Four significant peak tensions on the needle thread tension trace and two significant peak tensions on the bobbin thread tension trace were detected, during a stitch cycle. It was found that no significant variations occurred as far as the timing and shape of the peak tensions were concerned. However, variations were detected in the peak tensions according to the sewing conditions, as expected. From the analysis of the data obtained, multiple regression equations were derived to predict, with a good degree of accuracy, the peak tensions generated, according to the sewing conditions.

Transient Torque Produced in Arm Shaft of an Industrial Sewing Machine

This study considered the effects of needle penetrating force, needle thread tightening tension, and pressing force of the presser foot on torque produced in the arm shaft of an industrial sewing machine. The results obtained are as follows. (1) Penetrating force, especially the initial triangular wave fluctuation, induces noticeable transient vibration in torque. (2) The penetrating force is considerably more transient than the pressing force. The time ratio of the duration of the penetrating force to the natural period of the motion system is close to 1. (3) Consequently, when estimating torque, it is necessary that the arm shaft of the thread take-up lever and needle bar mechanism motion system be considered as elastic. On the other hand, the arm shaft of the feed mechanism motion system can be treated as a rigid body.